docs: def to_auto_download_state(arg):
      '''
      to_auto_download_state(arg) attempts to coerce the given argument into a valid auto-downloading
        instruction. Essentially, if arg is "on", "yes", "true", "1", True, or 1, then True is
        returned; if arg is "structure" then "structure" is returned; otherwise False is returned.
      '''
      if pimms.is_str(arg):
          arg = arg.lower().strip()
          if arg in ('on', 'yes', 'true', '1'): return True
          elif arg in ('struct', 'structure', 'structural'): return 'structure'
          elif arg in ('retinotopy', 'retino', 'ret'): return 'retinotopy'
          else: return False
      return arg in (True, 1)